International Usage
In the United Kingdom it is called the ringer equivalence number and a maximum of 4 is allowed on any British Telecom (BT) line.
In Australia it is also called ringer equivalence number and a maximum of 3 is allowed on any Telstra or Optus Line.
In Canada it is called a Load Number (LN); which cannot exceed 100. (The LN of each device represents the percentage of total load allowed).
In Europe 1 REN used to be equivalent to an 1800Ω resistor in series with a 1 µF capacitor. The latest ETSI specification (2003-09) calls for 1 REN to be greater than 16 kΩ at 25 Hz and 50 Hz.
Read more about this topic: Ringer Equivalence Number
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